The present invention relates to a developer solution for a photoresist composition or, more particularly, to a developer solution for alkali-developable positive- and negative-working photoresist compositions widely used in the photolithographic precision-patterning works in the manufacture of various kinds of semiconductor devices.
As is well known, it is a well established technology in the electronics industry that a finely patterned resist layer is formed by the photolithographic method on the surface of a substrate such as semiconductor silicon wafers in the manufacturing process of various kinds of semiconductor devices such as ICs, LSIs and the like. In the photolithographic patterning process, a layer of a photosensitive composition formed on the substrate surface is exposed patternwise to actinic rays such as ultraviolet light to form a patterned latent image which is then developed to give a patterned resist layer by using a suitable developer solution which is a weakly alkaline aqueous solution when the photosensitive composition is an alkali-developable photosensitive resin composition. It is usual that the alkaline developer solution contains an organic base free from any metallic element such as tetramethyl ammonium hydroxide, choline and the like in consideration of the possible adverse influences caused on the performance of the semiconductor devices by the metallic contaminant coming from the developer solution.
Among the various requirements which a developer solution for a photoresist composition should satisfy, it is very important that the substrate surface bearing the patterned resist layer after development is absolutely free from scums produced in the development treatment since even a slightest deposition of scums on the patterned resist layer would have a very serious adverse influence on the quality of the semiconductor device manufactured by subsequent processing.
Various attempts and proposals have been made heretofore in order to minimize occurrence of scums on the patterned resist layer after development by modifying the nature of the developer solution with the admixture of a specific additive. An additive agent of the most widely used class in this regard is a surface active agent including anionic surface active agents such as alkyl-substituted diphenyl ether ammonium sulfonates disclosed in Japanese Patent Kokai No. 4-204454 and non-ionic surface active agents such as polyoxyethyleneglycol mono(alkylphenyl) ethers disclosed in Japanese Patent Kokai No. 63-25650.
Even if not to mention that occurrence of scums cannot be completely prevented by using a developer solution admixed with these surface active agents, another problem in the use of a surface active agent in the developer solution is that, while it is highly desirable that the cross sectional profile of the line pattern of the resist layer formed by the development treatment is orthogonally upright on the substrate surface with square shoulders, the shoulder portion of the line pattern of the resist layer formed by using such a developer solution is sometimes rounded.
Besides the above mentioned problems relative to the performance of the developer solutions, it is a trend in the photolithographic technology in recent years that improvement in the reproducibility and productivity of the patterning works is desired by using materials which ensure a larger latitude of light exposure dose and wider depth of focus than in the use of conventional materials. These parameters naturally depend on the performance not only of the photosensitive resin composition but also of the developer solution so that, along with the improving efforts of the photosensitive resin composition, it is eagerly desired to have a developer solution capable of giving improvements relative to these parameters. None of the developer solutions proposed heretofore, however, can be quite satisfactory in this regard.